U.S. patent number 4,511,022 [Application Number 06/457,576] was granted by the patent office on 1985-04-16 for valve arrangement for regulating vehicle suspension damping pressures.
This patent grant is currently assigned to Lucas Industries. Invention is credited to Stanley G. Glaze, Alan Thomas.
United States Patent |
4,511,022 |
Thomas , et al. |
April 16, 1985 |
Valve arrangement for regulating vehicle suspension damping
pressures
Abstract
A valve arrangement for regulating damping pressure on a piston
in a vehicle suspension comprises two identical valves in series
between opposite sides of the piston. The valves are moved in
unison in response to an intermediate pressure between them and by
a servo pressure regulated by a further valve which is responsive
to the intermediate pressure and to a current signal supplied to a
torque motor. The arrangement is a closed system in which damping
force is proportional to torque motor current.
Inventors: |
Thomas; Alan (Stratford on
Avon, GB2), Glaze; Stanley G. (Brierley Hill,
GB2) |
Assignee: |
Lucas Industries
(GB2)
|
Family
ID: |
10527738 |
Appl.
No.: |
06/457,576 |
Filed: |
January 13, 1983 |
Foreign Application Priority Data
|
|
|
|
|
Jan 20, 1982 [GB] |
|
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8201550 |
|
Current U.S.
Class: |
188/266.5;
188/312; 267/64.28 |
Current CPC
Class: |
B60G
17/0152 (20130101); F16F 9/465 (20130101); B60G
2500/11 (20130101); B60G 2600/184 (20130101); B60G
2500/112 (20130101) |
Current International
Class: |
B60G
17/015 (20060101); F16F 9/44 (20060101); F16F
9/46 (20060101); F16F 009/20 () |
Field of
Search: |
;188/279,285,299
;267/64.11,64.28 ;280/707,714 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Reger; Duane A.
Attorney, Agent or Firm: Andrus, Sceales, Starke &
Sawall
Claims
We claim:
1. A valve arrangement for regulating the pressures on opposite
sides of a damping piston in a road vehicle suspension, said valve
arrangement comprising two identical valve devices in series and
connected, in use, between zones on opposite sides of said damping
piston, said devices including substantially identical flow control
elements which are coupled for movement in unison so that the
effective flow areas of the devices are substantially equal to each
other in all operating positions of their flow control elements and
the fluid pressure intermediate the devices is substantially equal
to the arithmetic mean of said pressures on opposite sides of the
damping piston, a further valve for regulating a servo pressure in
accordance with the magnitude of said intermediate pressure and the
magnitude of an electrical input signal, and means for positioning
said flow control elements in response to said servo pressure so
that, for a given value of said input signal a change in said
intermediate pressure causes said servo pressure to move said
control elements in a sense to oppose said change, whereby said
intermediate pressure, and hence the force acting on said damping
piston, is dependent on the magnitude of said electrical input
signal.
2. A valve arrangement as claimed in claim 1 which includes
passages for connecting said valve devices in series between
chambers on opposite sides of said damping piston, and means for
returning fluid from said further valve to whichever of said
passages is at the lower pressure.
3. A valve arrangement as claimed in claim 1 in which said valve
devices comprise lands on a spool, one end of said spool being
subjected to said servo pressure, and the other end thereof to said
intermediate pressure.
4. A valve arrangement as claimed in claim 1 in which said servo
pressure is derived by said further valve from said intermediate
pressure.
5. A valve arrangement as claimed in claim 1 in which said further
valve comprises a control member responsive to an actuating
pressure derived from said intermediate pressure, and a torque
motor for urging said control member against said actuating
pressure.
6. A valve arrangement as claimed in claim 5 in which said control
member comprises a spool whose opposite ends are acted upon by said
actuating pressure and said torque motor.
7. A valve arrangement as claimed in claim 5 in which said control
member comprises a lever urged in respective opposite directions by
said servo pressure and by said torque motor.
Description
It has been proposed, for example in U.S. Pat. No. 4,030,580, to
control electrically the damping applied to wheel carriers in a
road vehicle, to obtain desired vertical displacement and/or
acceleration characteristics of a vehicle body relative to the
ground. The aforesaid U.S. patent discloses a hydraulic damping
device in which fluid flow between opposite sides of a damper
piston is regulated by an electro-hydraulic servo valve and in
which operating pressure for the servo valve is obtained from
displacement of the damping fluid, whereby no external hydraulic
pressure source is required.
It is a disadvantage of the aforesaid prior art device that the
servo valve is positioned only in accordance with a controlling
electrical current, and is not directly responsive to the pressures
on the damper piston. It is required that the force on the damper
piston shall be proportional to the controlling current. In the
prior art arrangements this result is obtainable only by rendering
the controlling current responsive to the sensed damping force,
thereby introducing an additional control loop. In the present
invention the servo valve is directly responsive to the damping
pressure as well as to the controlling current, whereby the
aforesaid additional control loop may be dispensed with.
It is an object of the present invention to provide a damping
device for a vehicle suspension in which the foregoing advantages
are present.
According to the invention there is provided a valve arrangement
for regulating the pressures on opposite sides of a damping piston
in a vehicle suspension, said valve arrangement comprising two
substantially identical valve devices having control elements which
are coupled for movement in unison so that the effective flow areas
of said devices are substantially equal in all operating positions
thereof, said control elements being responsive to a servo pressure
signal, and a further valve responsive to a fluid pressure
intermediate said valve devices and to an electrical input signal,
for regulating said servo pressure signal.
Embodiments of the invention will now be described, by way of
example only, and with reference to the accompanying drawings, in
which:
FIG. 1 is a diagram of a vehicle wheel suspension and damping
device; and
FIG. 2 is a diagram of a modified form of the suspension shown in
FIG. 1.
As shown in FIG. 1 a carrier 10 for a vehicle wheel 11 is mounted
on a fixed part of the vehicle body and coupled to a piston 12
which is slidable in a cylinder 13. The piston and cylinder 12, 13
act to damp movement of the carrier 10 and wheel 11, and chambers
14, 15 in the cylinder 13 on opposite sides of the piston 12 are
interconnected through a passage 16, a valve arrangement 17 and a
further passage 18.
The valve arrangement 17 includes a valve spool 20 having two
identical lands 21, 22 which co-operate with respective ports 23,
24 to provide two identical valve devices, the arrangement being
such that in all positions of the spool 20 the effective flow areas
of the ports 23, 24 are equal. The valve device 21, 23 and 22, 24
are interconnected through a passage 25. Ends 26, 27 of the spool
20 have respective cross-sectional areas a, A, such that A=2a. An
intermediate pressure Pi in the passage 25 thus acts on the land 22
over an effective area a.
A further, pilot valve 28 incudes a valve spool 29 which is
subjected to the pressure Pi in the passage 25, through a
restrictor 31, an increase in pressure Pi urging the spool 29 to
connect a chamber 32 of the spool valve 20 to a low pressure return
line 33 and thus to reduce a servo pressure Ps actong on the end 27
of the spool 20. The pilot valve spool 29 is urged against the
pressure Pi by a lever 34 acted on by a torque motor 35. The
arrangement is such that in equilibrium, when the force on the
spool 29 from the torque T of the motor 35 is balanced by the force
applied by the pressure Pi, the chamber 32 is isolated from both
the pressure Pi and the return pressure in line 33. Non-return
valves 36, 37 ensure that the line 33 communicates with whichever
of the passages 16, 17 is at the lower pressure. A reservoir 38
communicates with the line 33 and maintains the system full of
fluid. Springs 39, 40 maintain the spool 20 in an equilibrium
position in the absence of hydraulic pressures thereon.
When the wheel 11 is moving downwardly, as viewed in the drawing,
the higher damping pressure PD will exist in the chamber 15 and the
passage 18, and a lower pressure PL in the chamber 14 and passage
18. Since the effective flow area of the valve 21, 23 is equal to
that of the valve 22, 24 then
and for equilibrium of the pilot valve 28
where k is a factor dependent on the valve geometry and T is the
torque exerted by the torque motor 35 and is proportional to the
magnitude of the current supply thereto. Since the pressure PL is
always very low, being equal to the head of liquid in the reservoir
38, from (1) and (2) above
that is, the damping pressure PD is, for practical purposes,
proportional to the torque of the motor 35, and hence to its input
current.
With a constant torque T from the motor 35, an increase in pressure
PD results in an increase in the intermediate pressure Pi applied
to the area a of the land 22, and the spool 29 moves rightwards,
reducing the pressure Ps and allowing the spool 20 to move
rightwards. Flow from the chamber 15 to the chamber 14 increases
until the difference between the pressures in these chambers falls.
The intermediate pressure Pi also falls to a value consistent with
the torque T of the motor 35. In this condition the spool 29
returns to its equilibrium position, and the damping pressure PD is
again proportional to the torque T.
It will be apparent that, since the intermediate pressure Pi is, as
indicated in equation (1) above, independent of the direction of
fluid flow through the valve devices 21, 23 and 22, 24, damping
pressure PD will be approximately proportional to the torque T,
independently of whether the pressure PD occurs in the chamber 14
or the chamber 15 of the damping cylinder.
It will also be apparent that the damping pressure PD, for either
direction of movement of the wheel 11, may readily be varied by
means of the torque motor 35.
The suspension shown in FIG. 2 is generally similar to that of FIG.
1, but has a flapper control element for its pilot valve instead of
a spool.
A carrier 110 for a vehicle 111 is mounted on a fixed part of the
vehicle body and coupled to a piston 112 which is slidable in a
cylinder 113. The piston and cylinder 112, 113 act to damp movement
of the carrier 110 and wheel 111, and chambers 114, 115 in the
cylinder 113 on opposite sides of the piston 112 are interconnected
through a passage 116, a valve arrangement 117 and a further
passage 118.
The valve arrangement 117 includes a valve spool 120 having two
identical lands 121, 122 which co-operate with respective ports
123, 124 to provide two identical valve devices, the arrangement
being such that in all positions of the spool 120 the effective
flow areas of the ports 124, 124 are equal. The valve devices 121,
123 and 122, 124 are interconnected through a passage 125. An end
126 of the spool 120 has a cross-sectional area a and the other end
127 of the spool 120 has a cross-sectional A, such that A=2a. An
intermediate pressure Pi in the passage 125 thus acts on the lands
121, 122 over effective areas a in each case.
The passage 125 communicates with a pilot valve 130 through a flow
restrictor 131. The end 127 of the spool 120 is subjected to a
servo pressure Ps intermediate the valve 130 and restrictor 131.
The pilot 130 has a lever control element 132 and a torque motor
134, an increase in torque from the motor 134 urging the element
132 against force applied thereto by the pressure Ps. The
downstream side of the valve 130 communicates through a passage 135
with a chamber 136 at the end 126 of the spool 120. A shuttle valve
137 ensures that the pressure PL in the passage 135 is that of the
lower of the pressures in the passages 116, 117. Light springs 138,
139 maintain the spool 120 in an equilibrium position in the
absence of hydraulic pressures thereon. A reservoir 140 maintains
the system full of fluid.
If the wheel 111 is moving downwardly, as viewed in the drawing,
then the higher, damping pressure PD will exist in passage 118 and
the lower pressure PL in passage 116. As before the effective flow
areas of the valves 121, 123 and 122, 124 are equal, and
intermediate pressure
In equilibrium of the spool 120 the forces thereon as a result of
hydraulic pressure are given by
In equilibrium of the element 32 the torque T from the motor 34 is
given by
where k is a factor dependent on the geometry of the valve 130.
Since PL is a very low pressure, corresponding to the head of
liquid in the reservoir 140,
from (4) Pi.apprxeq.PD/2
and from (6) kT.apprxeq.PS
substituting in (5)
a PD/2.apprxeq.2akT
whereby PD.apprxeq.4kT.
So that the damping pressure PD is approximately proportional to
the torque T applied by the motor 134.
It will be apparent that, since the intermediate Pi is, as
indicated in equation (1) above, independent of the direction of
fluid flow through the valve devices 121, 123 and 22, 24, damping
pressure PD will be approximately proportional to the torque T,
independently of whether the pressure PD occurs in the chamber 114
or the chamber 115 of the damping cylinder.
With the wheel 111 moving downwardly the damping pressure PD will
exist in the chamber 115 and passage 118. With a constant torque T
from the motor 134, an increase in pressure PD results in an
increase in the intermediate pressure Pi applied to the area a of
the land 122, and an increase in the servo pressure Ps applied to
the area A at the end 127 of the spool 120. Since the pressure Ps
is substantially less than the pressure Pi, there is initially no
significant movement of the spool 120. However, the increase in
pressure Ps moves the element 132 to increase flow through the
valve 130, thereby reducing the servo pressure Ps and permitting
the spool 120 to move to the right, thereby increasing flow from
the chamber 115 to the chamber 114 until the difference between
these pressures falls to a value consistent with the torque T of
the motor 134. In this condition the control element 132 returns to
its original position and the device is once again in
equilibrium.
* * * * *